Organometallics 1995,14, 1681-1687
1681
Chains and Stars in Organoplatinum Oligomers Sudhir Achar and Richard J. Puddephatt* Department of Chemistry, University of Western Ontario, London, Canada N6A 5B7 Received December 6, 1994@
A method for synthesis of new oligomers and a polymer containing organoplatinum centers is reported. Reaction of [PtMe~(buzbipy)l,lb, buzbipy = 4,4’-di-tert-butyl-2,2’-bipyridine,
with 4-(bromomethy1)-4‘-methyL2,2’-bipyridine,A, gave the complex [PtBrMez(buzbipy)2,M by~oxidative addition of the C-Br bond to platinum(I1). Reaction (CHZC~H~NC~H~N )], of 2 with [PtzMe4(~A3Mez)z],B, gave the PtrvPtI1complex [PtBrMe~(bu~bipy)@CH~C5H3NCsH3NMe)PtMezI, 3, by displacement of the MezS ligands from B by the free bipyridine group of 2 to regenerate a reactive dimethylplatinum(I1) center. Repetition of this cycle of reactions gave [PtBrMez(buzbipy){O(-CH~C~H~NC~H~NM~)P~B~M~Z}.(CHZC~H~NC~H~N (4, n = 1; 6, n = 2) and [PtBrMez(buzbipy){O(-CHZC~H~NC~H~NM~)P~B~M~Z).@CHZC~H~NC5H3NMe)PtMezl (5, n = 1; 7, n = 2). Reaction of A with B gave the insoluble polymer [{P~B~M~Z(D-CHZC~H~NC~H~NM~)}.I. Star-shaped oligomers containing platinum(rV) centers were obtained by reaction of 1,2,4,5-(BrCH~)4C6H~ with the complexes 1,3,or 5 to give ~ , ~ , ~ , ~ - [ P ~ B ~ M ~ ~ ( ~ U ~ ~ ~ ~ ~ ) { ( D - C H Z C ~ H ~ N C ~ H(n~=N0, Mlob; ~ ) Pn~=B ~ M ~ Z } ~ C H Z I 1, 11; and n = 2, 12,respectively).
Introduction There is considerable current interest in the design and synthesis of oligomers and polymers having novel linear or branched structural features, which in the future may prove useful in “nanostructures”, supermolecules, and new types of polymers.’ The development of new strategies for synthesis of organic, organometallic, and inorganic compounds with branched structures of either “star” or “dendrimer” architecture has been a prominent feature in the explosive growth of this field.’ It is a particular challenge in inorganic and organometallic chemistry where techniques for stepwise growth of oligomeric structures are still relatively undeveloped. There are a number of potential applications, for example as light harvesting antennae.’ The project described below addresses the problem of how oligomeric organometallic compounds with “star” structures can be synthesized. Complexes of the type [PtMez(NN)I,1, in which NN represents a diimine ligand such as 2,2’-bipyridine, are very reactive in oxidative addition of alkyl halides, and this reaction has been used to synthesize many functionally substituted organoplatinum(r\r) complexes. For example, introduction of vinyl groups is easy and can give useful monomers for free radical initiated polymerization, yielding organoplatinum(rV)polymers, while use of bifunctional alkyl halides can give hydrocarbylbridged binuclear organoplatinum(n7) complexes.2 The diimine complexes 1 are themselves easily prepared by displacement of MezS ligands from [PtzMe4(p-SMe~)zl.~ The sequence of reactions leading to functionally substituted organoplatinum(IV) complexes is shown in eq 1,R = functional substituent. If the group R contained
’
@Abstractpublished in Advance ACS Abstracts, March 1, 1995. (1) (a) Mekelburger, H.-B.; Jaworek, W.; Vogtle, F. Angew. Chem., Int. Ed. Engl. 1992,31,1571.(b) Webber, S.E. Chem. Rev. 1990,90, 1469.(c) Juris, A.; Balzani, V.; Campagna, S.; Denti, G.; Serroni, S.; Frei, G.; Gudel, H. U. Znorg. Chem. 1994,33, 1491.(d) Seebach, D.; Lapierre, J. M.; Greiveldinger, G.; Skobridis, K. Helu. Chim. Acta 1994,
77,1673.
a diimine group, it follows that a second dimethylplatinum(I1) group could be introduced and that repetition of the sequence could give organoplatinum oligomers. An adaptation of this method has recently been used t o synthesize several oligomeric organoplatinum dendrimers, containing up to 28 platinum atoms.3 This article shows how oligomeric organoplatinum(N) complexes in the form of chains or stars can be synthesized by using the basic reactions of eq 1with the alkyl halide being 4-(bromomethyl)-4‘-methyl-2,2’-bipyridine.
Results and Discussion Synthesis of Chain Oligomers. The synthesis of the chain oligomers is outlined in Scheme 1. The platinum(I1) complex [PtMez(bu2bipy)l7lb, buzbipy = 4,4’-di-tert-butyl-2,2’-bipyridine, was chosen as the plat(2)(a)Jawad, J. K.; Puddephatt, R. J. Organomet. Chem. 1976,117, 297.(b) Jawad, J. K.; Puddephatt, R. J. J. Chem. Soc., Dalton. Trans. 1977,1466.(c) Ferguson, G.;Parvez, M.; Monaghan, P. K.; Puddephatt, R. J. J. Chem. SOC.,Chem. Commun. 1983,267.(d) Monaghan, P. K.; Puddephatt, R. J . Organometallics 1984,3,444.(e) Monaghan, P.K.; Puddephatt, R. J. Organometallics 1986,4 , 1406. (0 Scott, J . D.; Puddephatt, R. J. Organometallics 1986, 5 , 1538. (g) Crespo, M.; Puddephatt, R. J. Organometallics 1987,6, 2548. (h) Monaghan, P. K.; Puddephatt, R. J. J. Chem. SOC.,Dalton. Trans. 1988,595.(i) Aye, K.T.; Canty, A. J.; Crespo, M.; Puddephatt, R. J.; Scott, J. D.; Watson, A. A. Organometallics 1989,8,1518.(i) Scott, J. D.; Puddephatt, R. J . Organometallics 1983,2,1643.(k) Achar, S.; Scott, J. D.; Puddephatt, R. J. Organometallics 1992,11,2325. (1) Achar, S.;Scott, J. D.; Vittal, J. J.; Puddephatt, R. J. Organometallics 1993,12,4592. (3)(a) Achar, S.; Puddephatt, R. J. Angew. Chem., Znt. Ed. Engl. 1994,33,847.(b) Achar, S.;Puddephatt, R. J. J. Chem. SOC.,Chem. Commun. 1994,1895.
0276-733319512314-1681$09.00/0 0 1995 American Chemical Society
Achar and Puddephatt
1682 Organometallics, Vol. 14, No. 4, 1995 Scheme 1
inum(11) substrate since the buzbipy ligand gives complexes with higher solubility than the corresponding complexes of 2,2'-bipyridine. Complex lb is orange red in color due to the presence of a platinum(5dFdiimine(x*) metal to ligand charge transfer (MLCT)band in the visible region: and the platinum(IV1 products of oxidative addition are colorless or pale yellow since the MLCT band is shifted to higher energy. Hence reactions are easily monitored by visible spectroscopy or simply by observing the bleaching of color as the platinum(I1) complex is consumed. The CH2-Br group of the reagent 44bromomethyl)4'-methyL2,2'-bipyridine, A,added rapidly to lb to give the pale yellow platinum(N) complex 2. The stereochemistry of the product 2 was established from the 'H NMR spectrum. There was a single MePt resonance, a single t-Bu resonance and a single CHzPt resonance. Hence there must be a mirror plane and the product must be formed by trans oxidative addition. Close inspection showed the presence of two very low intensity ~~
~
~
(4) Chaudhury, N.; Puddephatt, R.
84,105.
MePt resonances, assigned to a trace amount (ca 3%) of the product of cis oxidative addition, 2. No other resonances of the minor product were resolved, but all resonances of the major isomer were easily identified and assigned (see the Experimental Section). The protons H3a,H5a,and H6a (see structure 2 in Chart 1) appear in the unusual chemical shift range 6 = 6.57.1 whereas H3b, H5b, and H6b have more typical aromatic proton chemical shifts in the range 6 = 7.98.4. The assignment of the H3" and H5" resonances is confirmed by the observation of satellites due to coupling to lg5Pt,with 4J(PtH)= 11and 12 Hz,respectively. The pattern of aromatic chemical shifts IS attributed to the complex having a preferred conformation with the pyridyl group containing H3a-H6a lying under the buzbipy ligand where the ring current effect can lead to shielding of the aromatic protons. A similar effect has been observed for some related benzylplatinum(N) complexes.2,5 The complex [PtzMe&-SMe2)21, B, is a convenient
J. J . Organomet. Chem. 1975,
( 5 ) Byers, P. K.; Canty, A. J.J. Chem. Soc., Chem. Commun. 1988,
639.
Chains and Stars in Organoplatinum Oligomers
Chart 1
6b
5b
2'
0
source of MezPt" units by displacement of the SMe2 ligandse2 Thus the free bipyridine substituent in 2 can act as a ligand to displace Me2S from B to give the mixed oxidation state PtTVPt"complex 3. Since a new bipyridine platinum(I1) center is formed in this reaction, a color change from very pale yellow to red-orange is observed, due to a MLCT band in the visible region [platinum(II)5d-~r*(diimine)l.~ Many features of the 'H NMR spectrum of 3 are similar to those in complex 2, with the spectrum of 3 having two extra singlet resonances due to the new Me&" group, each having satellites due to coupling to lg5Pt with V(PtH) = 83 Hz2 Again, all resonances were sharp and well-resolved and h l l assignments are given in the Experimental Section. The FAB mass spectrum of 3 displays peaks due t o [M 21 and [M - (Br 2Me)l. The synthesis of complex 3 represents the end of the first growth cycle in which a dimethylplatinum(I1) center undergoes oxidative addition, followed by generation of a new dimethylplatinum(I1) center which is then able t o participate in the next cycle (Scheme 1). The reaction between 3 and A gave the P t V P complex 4, which was easily isolated as a pale yellow solid. Unlike 2 and 3,complex 4 cannot contain a plane of symmetry and so the lH NMR spectrum is considerably more complex. The spectrum contained two singlets due to the t-Bu groups at 6 = 1.29 and 1.41, four MePtTV resonances a t 6 = 1.20, 1.23, 1.53, and 1.57 each with satellites due to coupling to lg5Ptwith 2J(PtH)= 6970 Hz and two singlets due to the MeC groups at 6 = 2.21 and 2.38. The CH& groups each gave an "AB" pattern, with overlapping peaks in the region 6 = 2.453.00; nonequivalence of the CHaHbPtprotons is expected as a result of the lower symmetry of 4. The aromatic protons of the bipyridine groups appeared at 6 = 6.08.8; 18 resonances are expected, but only 12 were resolved as separate peaks so full assignment was not attempted. The mass spectrum of 4 failed to show a molecular ion peak at m f z = 1242,but the highest mass
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Organometallics, Vol. 14,No.4,1995 1683
observed was at m l z = 1212 due to loss of two methyl groups. Complex 4, dissolved in benzene, reacted with B to give the red complex 5, thus completing the second growth cycle. Complex 5 is a trinuclear PtIV2Pt" complex. The 'H NMR spectrum was similar to that of 4 but with two additional resonces due to the Me2Pt1I group a t 6 = 0.70 and 0.82, each with WPtH) = 82 Hz. In principle, the growth cycles should be capable of repetition to grow continually larger organoplatinum oligomers, but problems arise as the molecules grow in size. First, there is a general decrease in solubility with chain length, following the sequence 1 > 2 > 3 > 4 > 5. All have reasonable solubility in dichloromethane, but those containing Pt" centers react slowly with this solvent by oxidative addition of a C-C1 bond to the platinum(I1) center,2 and so this solvent cannot be used for synthetic reactions. Complexes 1, 2, and 3 are soluble in acetone but 4 and 5 are not. Complex 4 is soluble in benzene and 5 is soluble in acetonehenzene mixture though not in either solvent alone. Characterization by lH NMR and by FAB MS becomes more difficult as the molecular size increases further. We have completed one further growth cycle to give complexes 6 and 7 (Chart 21, but characterization of these complexes is less secure than for the complexes 1-5. For example, in the 'H NMR spectrum of 6, the three MeC resonances were resolved but the M e P P groups overlapped and were not clearly resolved. There was no MePt" resonance and the complex was pale yellow, thus proving that the oxidative addition reaction occurred quantitatively. Complex 7 was sparingly soluble in all common organic solvents and was clearly unsuitable as a precursor to further growth cycles. Synthesis of an Organoplatinqm Polymer. Reaction of the dimethylplatinum(I1) complex B with reagent A occurred to give a red solution, which then became purple in color and finally became paler as a yellow powder precipitated from solution. This solid 8.~ H ~ N M ~ ) analyzed as [ ( P ~ M ~ z B ~ ( C H ~ C ~ H ~ N C These results are interpreted in terms of the reactions shown in Scheme 2. The first step involves displacement of SMe2 from B by the bipyridyl group of A. This yields a dimethylplatinum(I1) complex with an appended CHzBr group, 9. The geometry does not allow intramolecular oxidative addition t o occur so intermolecular oxidative addition occurs instead. The dimethylplatinum(I1)groups which give rise to the intense colors are then consumed, and the polymeric platinum(W product eventually precipitates. Monitoring by lH NMR at low temperature did not indicate any buildup of a long-lived intermediate. Hence it is deduced that the intermediate dimethylplatinum(I1) complexes undergo oxidative addition at a rate competitive with their formation. The polymer was insoluble in acetone, benzene, and chlorinated solvents but did dissolve in dimethyl sulfoxide. A lH NMR spectrum of the polymer in dmso-ds contained broad peaks characteristic of organoplatinum polymers. There were resonances in the aromatic and aliphatic regions having the expected intensities, but individual resonances were not resolved. There were no signals in the region 6 = 4-5 implying that all the bromomethyl groups had undergone the oxidative addition reaction. Because of the low solubility, the molecular weight of the polymer could not
Achar and Puddephatt
1684 Organometallics, Vol. 14, No. 4, 1995 Chart 2
twelve platinum atoms, respectively, as shown in Scheme be determined. Scheme 2 shows the first proposed 3. The lH NMR spectra of these complexes contained intermediate, a possible next step, and the final polymer only broad, poorly resolved resonances, but the integrain idealized form. tion of the spectra, together with the analytical data, Synthesis of Star-Shaped Platinum(W Comsupported the proposed formulations. For example, the plexes. In the synthesis of dendrimeric organoplatispectrum of 11 gave envelopes of peaks at 6 = 0.6-1.8 num(IV) complexes, it was found that the solubility of the products increased with increasing b r a n ~ h i n g . ~ (120 H, MePt t-Bu), 2.1-3.2 (28H, CH2Pt MeC) and 6.0-8.8 (50H, aromatic protons). The lg5PtNMR specTherefore, an attempt to synthesize more soluble olitrum contained two resonances of equal intensity, a gomers by introducing branching was made. The sharp resonance at 6 = -911 [with three partly resolved results are shown in Scheme 3. The key reagent for components at 6 = -908, -911, -9131 and a broad this work is 1,2,4,5-tetrakis(bromomethyl)benzene, C, resonance at 6 = -855. We suggest that the conformawhich can react with four organoplatinum(I1) centers unit P ~is) ~rigidly fixed but that tion of the C G H ~ ( C H ~ by oxidative addition of the C-Br bonds. Reagent C more than one conformation of the outer shell of reacted with [PtMez(bipy)l, bipy = 2,2'-bipyridine, t o organoplatinum(IV) groups is possible, leading to nongive the product [1,2,4,5-(PtBrMe2(bipy)CH2}&6H21, equivalence. Because of steric hindrance to rotation loa, which was very sparingly soluble. Fortunately, the about the CsH2-CH2 and CH2-Pt bonds, these less corresponding product, lob, from [PtMedbu2bipy)lwas symmetrical conformations are essentially frozen on the soluble and was readily characterized by NMR. The lH NMR time scale and lead to broad resonances in both NMR spectrum contained two MePtN resonances at 6 the 'H and lg5PtNMR spectra. Complex 12 contains a = 0.77 and 0.88, each with 2J(PtH)= 68 Hz, and the CH2Pt group gave rise to an "AB" spectrum with 6 = total of 516 atoms and has a calculated molecular weight of 6330. It is considerably more soluble than the linear 2.15 [2J(PtH)= 91 Hz, 2J(HH) = 8 Hzl and ca. 1.5 [partly obscured by a t-Bu resonance. The nonequivaprecursor 5, presumabIy as a result of the increased lence of the MezPt and CHzPt protons is expected since branching. In order to obtain information about the size of the no plane of symmetry bisecting these groups is possible oligomers, GPC analysis of the platinum complexes 5, in 10. The lg5PtNMR spectrum of lob contained a sharp singlet at 6 = -870, thus proving the equivalence lob, 11, and 12 was carried out using THF solvent and of the four platinum atoms. Molecular mechanics polystyrene standards. The absolute molecular weights calculations, as well as simple steric considerations, cannot be expected to be correct since the standards are linear and organic while the complexes have heavy suggest a conformation with ortho CHzPt substituents mutually anti with respect t o the C6H2 ring as shown metal content and, for lob-12, are not linear. Neverthless, there is a correlation of the apparent molecular in Scheme 3. In a similar way, reaction of 3 or 5 with C gave the weight determined by GPC and the expected molecular star-shaped oligomers 11 and 12, containing eight and weight, although it is not a linear relationship as shown
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Chains a,nd Stars in Organoplatinum Oligomers
Organometallics, Vol. 14, No. 4, 1995 1685
Scheme 2
‘ , . . . A
B
J
in Figure 1. The data are fully consistent with the proposed formulations. Differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA) were carried out on the linear organoplatinum complexes 2-7 and on the polymer 8. DSC thermograms revealed that only the complexes 2 and 3 exhibited melting endotherms prior to decomposition. TGA studies on the above complexes (Table 1)indicated that all of them decomposed over a wide temperature range, in most cases leaving a residue of metallic platinum, confirmed by X P S and EDX analysis on the residue.
found in the reaction of Na[Co(CO)d with 1,2,4,5tetrakis(bromomethy1)benzene to yield 1,2,4,5-tetrakis((a-methylene)tetracarbonylcobalt)benzene,which possesses four cobalt center^.^ This is closely related to the method used in the present work, but combination of the star-forming reaction with the method of growing linear oligomers has made it possible to form higher molecular weight oligomers based on organoplatinum compounds. The synthesis of unusual mixed oxidation state complexes8 as well as a new type of organometallic polymerg is established in this work.
Experimental Section Conclusions A successful strategy for the step by step synthesis of linear, oligomeric organoplatinum complexes has been developed on the basis of oxidative addition reactions. The reactions occur in very high yield, but the ability to grow large oligomers is limited since the solubility decreases with chain length. An extension of the synthetic method gave the first examples of star-shaped multinuclear organoplatinum complexes. There are few examples of star type oligomers or polymers,lP6and most are organic in nature. An organometallic example is
The lH NMR spectra were recorded by using Varian Gemini 200 or XL-300spectrometers, and lg6Ptspectra (on the more soluble complexes only), by using the XL-300 spectrometer. Chemical shiRs are reported with respect to TMS or Kz[PtC41. Mass spectra were recorded by using a Finnigan MAT 8320 -
( 6 )Jerome, R.; Henrioulle-Granville, M.; Boutevin, B.; Robin, J. J.
Prog. Polym. Sci. 1991,16, 837. (7) Ullah, S.S.; h a m , K. A.; Hashem, M. A.; Ahmed, I.; Karim, M. M.; Khan, S.M. A. Indian J . Chem. 198’7,26A, 831. (8)Anderson, G. K.Adu. Organomet. Chem. 1993, 35, 1. (9) (a) Pittman, C. U., Jr. New Monomers and Polymers; Plenum Press: New York, 1984. (b) Tomalia, D.A.; Naylor, A. M.; Goddard, W. A., 111. Angew. Chem., Int. Ed. Engl. 1WO,29,138.
1686 Organometallics, Vol. 14,No. 4, 1995
Achar and Puddephatt Scheme 3
+
12
2500
/12
1
,0001 5 f b 500 1000
5000 Calculated MW
3000
7000
Figure 1. Graph of the calculated molecular weight of some platinum oligomers uersus the apparent molecular weights determined by GPC using linear polystyrene standards. mass spectrometer. Differential scanning calorimetry and thermogravimetric analysis were carried out employing Perkin-Elmer DSC7 and TGA7 instruments respectively. The heating rate was 20 "C/min, and a sample mass of 3-8 mg was used. Nitrogen was used as the purge gas. Gel permeation chromatography was performed on a Waters 600 GPC with Waters 410 differential refractometer as the detector. Millenium software was used to analyze the results. Two
Table 1. DSC and TGA Data for the Organoplatinum Compounds DSC, TGA,decomposn complex
melting onset
range and residue" ("C)
2
189 "C 194 "C does not melt does not melt does not melt does not melt
168-840,25 (26.7) 120-940,45 (39.7) 134-940.37 (31.4) 30-940, 53 (39.8) 220-940,40 (33.7) 119-940.40.3 (39.9)
3 4 5 6 8
Residue observed at the maximum temperature; the value if the residue were metallic platinum is enclosed in parentheses.
ultrastyragel columns were used in series (lo3and lo2A), and THF was used as the solvent. The system was calibrated with linear polystyrene standards. The complexes [PtzMe&SMez)zI2 and [PtMez(buzbipy)lZ and the diimine 4-(bromomethyl)-4'-methy1-2,2'-bipy1idine'~were prepared by literature methods. Complex 2. To a stirring red solution of [PtMez(bu~bipy)], lb, (0.10 g) in acetone (10 mL) was added 4-(bromomethyl)(10)Gould, S.; Strouse, G. F.;Meyer, T. J.; Sullivan, B. P. Inorg. Chem. 1991,30,2942.
Organometallics, Vol. 14, No. 4, 1995 1687
Chains and Stars in Organoplatinum Oligomers 4'-methyl-2,2'-bipyridine (0.06 g) in acetone (5mL). The color of the solution turned immediately to yellow. The solution was concentrated under vacuum, and the product was precipitated with pentane as a pale yellow solid. Yield: 88%. Anal. Calcd for C ~ Z H ~ ~ B C, ~N 50.8; ~ PH, ~ 5.5; : N, 7.4. Found: C, 50.8; H, 5.5; N, 7.3. Mass spectrum: m l z = 757 (12%)[MI+,676 (100%) [M - Br]+, 646 (80%)[M - (Br + 2Me)]+. lH NMR in CDzClz (300 MHz): 6 = 1.28 [S, 18H, t-Bu]; 1.48 [s,6H, 'J(PtH) 69 Hz, MezPt]; 2.35 [s, 3H, MeC]; 2.81 [s, 2H, WPtH) = 97 Hz, CHzPt]; 7.44 [dd, 2H, 3J(H6H5)= 6 Hz, 4J(H3H5)= 2 Hz, H5 of buzbipyl; 7.88 [d, 2H, 4J(H5H3)= 2 Hz, H3 of buzbipy]; 8.54 [d, 2H, 3J(PtH) = 12 Hz, 3J(H5H6)= 6 Hq, H6 of buzbipy]; 6.54 [dd, lH, 4J(H3H5)= 2 Hz, 4J(PtH) = 11 Hz, 3J(H6H5)= 5.5 Hz, H5" of CHzbipyMe]; 7.01 [m, lH, 4J(PtH) = 11Hz, H38of CHzbipyMe]; 7.06 [m, lH, 3J(H5H6)= 5.5 Hz, H6a of CHzbipyMe1; 7.92 [dd, lH, 3J(H6H5)= 5 Hz, H5bof CHzbipyMe]; 7.98 [s, lH, H3bof CHzbipyMel; 8.37 [dd, lH, 3J(H5H6)= 5 Hz, H6bof CHzbipyMe]; 6(Pt) = -940. In addition, resonances of much lower intensity (ca. 3%), corresponding t o the cis isomer were detected in the lH NMR at 6 = 1.19 and 1.39 [s, 3H each, WPtH) = 69 Hz, MePt], 2.78[s, 2H, CHzPtl. Complex 3. To a solution of complex 2 (0.07 g) in benzene (10 mL) was added a solution of [PtzMe4(p-SMez)zl(0.03g) in ether (10 mL). An instant change in color to red was observed. The mixture was cooled to 0 "C for 1 day, during which time the product precipitated as a red solid which was separated and washed with ether. Yield: 80%. Anal. Calcd for C34H47BrN4Ptz: C, 41.6; H, 4.8; N, 5.7. Found: C, 41.3; H, 4.8; N, 5.5. Mass spectrum: m l z = 984 (30%) [M 21+, 871 (28%) [M - (Br + 2Me)]+. lH NMR in CDzClz (200 MHz): 6 = 0.75 [s, 3H, V(PtH) = 85 Hz, MePt"]; 0.80 [s, 3H, V(PtH) = 83 Hz, MePt"]; 1.35 [s, 18H, t-Bul; 1.51 Is, 6H, V(PtH) = 69 Hz, MezPt]; 2.32 [s, 3H, MeCl; 2.82 [s, 2H, V(PtH) = 100 Hz, CHzPt]; 7.52 [dd, 2H, H5 of buzbipy]; 7.98 [d, 2H, H3 of buzbipyl; 8.56 [d, 2H, H6 of buzbipyl; 6.25 [m, lH, H5"of CHzbipyMe]; 7.04 [s, lH, H3" of CHzbipyMe]; 7.26 [d, lH, H6" of CHzbipyMe]; 7.4 [s, lH, H3bof CHzbipyMe]; 8.25 [d, lH, H5b of CHzbipyMel, 8.92 [d, l H , H6bof CHzbipyMe]. Complex 4. This was synthesized by reaction of complex 3 and BrCHzbipyMe by a similar procedure employed to synthesize the complex 2. Yield: 75%. Anal. Calcd for C46H58BrzN6Ptz: C, 44.5; H, 4.4; N, 6.8. Found: C, 43.6; H, 4.6; N, 6.5. Mass spectrum: m l z = 1212 (5%) [M - 2Me 1]+,1166 (50%)[M - 5Me)]+. 'H NMR in CDzClz (300 MHz): 6 = 1.29 and 1.41 [b, 9H each, t-Bul; 1.20 and 1.23 [s, 3H each, MezPtb]; 1.53 and 1.57 [s, 3H each, V(PtH) = 69 Hz, MezPt"]; 2.21 and 2.38 [s, 3H each, Me of CHzbipyMel; 2.45-3.1 [unresolved, 4H, 2CHzPtI; 6.0-8.8 [m, 18H, aromatic region]. Complex 5. To a solution of complex 4 (0.09 g) in benzene (12 mL) was added a solution of [PtzMe4(p-SMez)zl (0.025 g) in benzene (5mL). The solution turned red, and the product precipitated slowly. The red precipitate was separated from the solvent and washed with ether. Yield: 86%. Anal. Calcd for C48H&rzN&: C, 39.2; H, 4.4; N, 5.7. Found: C, 39.5; H, 4.5; N, 5.5. Mass spectrum: m l z = 1340 (40%) [M - (2 t-Bu + Me)]+, 1155 (100%)[M - (Pt+ 8Me)l+, 1126 (80%)[M - (Pt + 10Me) 11. Gel permeation chromatography: Apparent molecular weight = 600. 'H NMR in CDzClz (300 MHz): 6 = 0.70 and 0.82 [s, 3H each, 2J(PtH)= 82 Hz, MePtII]; 1.07 and 1.44 [s, 9H each, t-Bul, 1.21 and 1.23 [s, 3H each, MePtb]; 1.54 and 1.56 [s, 3H each, U(PtH) = 68 Hz, MePtal; 2.30 and 2.40 [s, 3H each, Me of CHzbipyMel; 2.45-3.25 [m, 4H, 2CH2Ptl; 6.1-9.0 [m, 18H, aromatic region].
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Complex 6. To a stirred suspension of complex 6 (0.075 g) in a 1:l mixture of acetone:benzene (25 mL) was added the diimine BrCHzbipyMe (0.015 g) in acetone (2 mL). The suspended solid dissolved to give a pale yellow solution. After 2 h, the solvent was removed and the product was washed with ether and dried. Yield: 82%. Anal. Calcd for C~oH75Br3N8P t 3 : C, 41.5; H, 4.3; N, 6.4. Found: C, 38.7; H, 4.2; N, 6.3. Mass spectrum: m l z = 1653 (100%) [M - Br]+, 1558 (55%) [M - (2Br Me)]+, 1482 (55%) [M - (2Br 6Me)l. lH NMR in benzene-& (200 MHz): 6 = 1.0-1.8 [m, 36H, MePt and t-Bul; 2.21,2.34, and 2.40 [s, 3H each, Me of CHzbipyMe]; 2.43.1 [m, 6H, CHzPt]; 5.5-9.0 [m, 24H, aromatic region]. Polymer 8. To a solution of [PtzMe4(p-SMez)zl(0.075g) in benzene (8 mL) was added a solution of 4-(bromomethyl)-4'methyl-2,Y-bipyridine(0.07 g) in benzene (5 mL). The solution turned red instantly, followed by a change to purple and finally pale yellow. The pale yellow precipitate which formed was separated and washed with ether. Yield: 71%. Anal. Calcd for (C14H17BrN~Pt)~: C, 34.4; H, 3.5; N, 5.7. Found: C, 33.9; H, 3.6; N, 5.3. lH NMR in dmsode (200 MHz): 6 = 0.8-1.8 [unresolved, 6H, MePt]; 2.0-3.0 [broad, partially hidden under the solvent peak, 5H, Me of CHzbipyMe and CHzPt]; 6.8-9.0 [broad, 6H, aromatic region]. Complex loa. To a stirring solution of [PtMez(bipy)l, l a (0.15 g), in acetone (10 mL) was added a solution of 1,2,4,5tetrakis(bromomethy1)benzene(0.045 g) in acetone (5 mL). The solution color changed from orange red to yellow. M e r the solution was stirred for an additional 4 h, the solvent volume was reduced and the precipitate was separated and washed c, with ether. Yield: 80%. Anal. Calcd for C58H66Br&%: 35.3; H, 3.4; N, 5.7. Found C, 35.0; H, 3.0; N, 6.0. FAB mass spectrum: m l z (%) = 1894 (10%)[M - Brl+; calcd [M - Brl = 1895. Similarly lob and 11 were prepared. Complex lob. Anal. Calcd for C ~ O H I ~ O B ~C,~ 44.6; N~P~~: H, 5.4; N, 4.6. Found: C, 43.8; H, 5.7; N, 4.3. 'H NMR in CDzClz(300 MHz): 6 = 0.65 [s, 12H, 2J(PtH)= 68 Hz, MezPt]; 0.88 [s, 12H, 2J(PtH)= 68 Hz, MezPt]; 1.45 [s, 72H, t-Bul; 2.1 [m, 4H, WPtH) = 91 Hz, CHzPtI; 7.52 [d, 8H, H5 of buzbipy]; 8.20 [s, 8H, H3 of buzbipyl; 8.26 [d, 8H, H6 of buzbipyl; 4.9 [m, CsHz]; 6(Pt) = -870. ~P~S: Complex 11. Anal. Calcd for C I ~ & ~ , B ~ ~ Nc ,I 40.1; H, 4.6; N, 5.1. Found: C, 39.1; H, 4.5; N, 4.9. lH NMR in CDzClz (300 MHz): 6 = 0.6-1.8 [br, 120H, MezPt and t-Bul; 2.1-3.2 [br, 28H, CHzPt and MeCl; 6.0-8.8 [br, 50H, aromatic region]; &Pt) = -855 [br, 4Ptl; -908, -911, -913 [s, 4Ptl. Complex 12. To a stirred suspension of 5 (0.150 g) in a 1:l mixture of acetone:benzene (100 mL) was added a solution of 1,2,4,5-tetrakis(bromomethyl)benzene(0.008 g) in acetone (2 mL). The suspended red solid dissolved to give a pale yellow solution. &r 1day, the solvent was removed and the product was washed with ether and dried. Yield: 95%. Anal. Calcd for CzozHz&rlzN2&12: C, 38.3; H, 4.2; N, 5.3. Found: C, 38.2; H, 4.2; N, 5.2. Gel permeation chromatography: Apparent molecular weight = 2500. lH NMR in dmSO-ds (200 MHz): 6 = 0.8-1.2 [br, 144H, MePt and t-Bu]; 2.1-3.0 [br, 48H, MeC and CHzPt]; 6.3-8.9 [br, 74H, aromatic region]; 6(Pt)= -871 [br, 4Ptl; -895 [br, 4Ptl; -906 [s, 4Ptl.
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OM940925L
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